Spatio-temporal rainfall trends in southwest Western Australia

Over the past several decades, there have been signi cant reductions in rainfall across southwest Western Australia. In the present work, the spatial and temporal structure of these reductions are investigated using generalized additive models. This involves smoothing over both space and time, to allow spatio-temporal interactions, as well as allowing for spatial correlation to ensure that standard errors are constructed appropriately for inference. The proposed method is computationally convenient as models are fitted as though di erent spatial locations are independent, and inference is subsequently adjusted for inter-site dependence. The results quantify precisely the spatially-varying nature of the decreasing rainfall trends.